1. Field of the Invention
The present invention relates to a temperature control system for a roller that is detachably mounted in a frame of an image forming apparatus. A primary liquid circuit is formed in the roller and contains a first liquid. A secondary liquid circuit is formed outside of the roller and contains a second liquid. A heat exchanger is arranged to bring the primary and secondary liquid circuits into thermal contact with one another and includes a first heat exchange member that is in thermal contact with the primary liquid circuit and projects outwardly from the roller.
2. Description of Background Art
In an image forming apparatus such as a printer, a copier or the like, several types of rollers need cooling or, more generally, temperature control during the image forming process. Such rollers include, for example, cooling rollers in a heat fuse station of a printer or the like, rollers supporting a photoconductor or a developing unit, guide and deflection rollers for image carrier belts, photoconductor drums or other image forming drums such as drums for a direct induction (DI) image forming process, and many more. It is preferable to use a liquid as a coolant or heat transfer medium, because a liquid dissipates more heat in high speed image forming apparatus and provides a more uniform temperature distribution within the roller. However, if the liquid coolant is circulated through the interior of the roller and through an external cooling device in order to permit efficient and uniform cooling, the coolant liquid circuit inside the roller has to be connected to an external circuit through a rotary seal. This makes it more difficult to detach the roller for maintenance or repair purposes or for exchanging the roller. This is particularly cumbersome for rollers that need to be exchanged regularly because their lifetime is shorter than the lifetime of the apparatus as a whole. In particular, there is a risk that coolant liquid leaks out when the roller is disconnected from or connected to the external circuit.
JP 60-122979 A discloses a temperature control system of the type indicated above, which has the advantage that the coolant may be permanently enclosed in an internal liquid circuit of the roller, so that it will not leak out when the roller is detached. In a preferred embodiment disclosed in this document, the heat exchanger is simply formed by cooling fins projecting from the roller, and the secondary or external coolant medium is simply formed by air that is blown against the cooling fins. Although this document mentions also the possibility that the secondary coolant medium may be a liquid, it does not disclose how a secondary liquid circuit could be configured so as to permit easy detachment of the roller. If the liquid of the secondary coolant circuit is to flow past the cooling fins of the roller, then there is still the problem that the liquid has to be sealed against the detachable roller.
JP-A-07049192 discloses a roll equipment and heating means for heating a hollow, rotating cylinder shaft of the roll equipment. The cylinder shaft has an end portion that is rotatably received in a heater, so that the end portion of the cylinder is heated by the heater. The cylinder shaft further contains a working liquid for distributing the heat in the cylinder.